Optical layer and light fixture with such an optical layer

ABSTRACT

An optical layer made from a light-permeable material includes a surface and an optical microstructure having a plurality of elevations. The elevations of the microstructure protrude from a reference plane, which is parallel to the surface. The elevations of the microstructure each have a flank section which adjoins the reference plane and forms a uniform angle with the reference plane. The uniform angle is in a range from about 10° to about 26° or in a range from about 13° to about 23° or in a range from about 15° to about 20°. The optical layer according to the invention makes it possible for a light fixture to achieve a high light output rate (LOR) at the same time to produce a preferred light distribution curve (LDC).

TECHNICAL FIELD

The invention relates to an optical layer according to the preamble ofindependent claim 1 and a light fixture having such an optical layer.Optical layers made from a light-permeable material having a surface andan optical microstructure, which comprises a plurality of elevations,wherein the elevations of the microstructure protrude from a referenceplane, which is parallel to the surface, can be used for anapplication-specific and efficient shaping of emitted and radiatedlight.

BACKGROUND OF THE INVENTION

Use of transparent lenses equipped with structures is known for adaptingand adjusting the light characteristics of light fixtures. In thisregard, the lenses cover one or more lighting means such that lightradiated from the lighting means penetrates the lens and is adapted bythis. For example, such an adaptation can include a directing of thelight, an attenuating of the light, a colouring of the light, adiffusing of the light or similar.

As is known, such lenses are produced by forming the structures directlyin a solid substrate of the lens. For example, the structures can be cutinto the substrate of the lens.

Another efficient means of preparing lenses is to provide alight-permeable substrate with an optical layer that adjusts light orillumination properties. The substrate here can be a transparent solidplastic, glass or the like. By providing the substrate with an opticallayer, it can be efficiently provided with application-orientedproperties. A lens as required can be produced in this way withrelatively little effort.

For example, layers are known which are applied to a substrate, forexample, adhesively bonded or fitted. The films themselves can alreadybe adhesive on one side or the films can be attached to the substrate ina manufacturing step of the lens by means of an additional adhesive.Such films are provided to diffuse or attenuate the light in someinstances.

An embodiment of such a film is described in WO 2012/141899 A1. The filmis produced from a light-permeable material and comprises a surface andan optical microstructure. The optical microstructure consists of aplurality of elevations, which protrude from the surface. The elevationsof the microstructure of the film are designed as cones, prisms orpyramids according to the teaching of WO 2012/141899 A1, the sides ofwhich have a random and varying base angle. This base angle correspondsto the angle between a direction orthogonal to the surface of the filmand to the associated side of the elevation. It should have a randomvalue between 10° and 60°. The lens provided with the film, firstly, issupposed to help the microstructure to suppress the glare of thepenetrating light by directing the light from the sides of theelevations of the microstructure. Secondly, the random base angle of theelevations is supposed to help make the light source less visible orcompletely invisible, which can be a concern in particular for LEDlighting means.

A disadvantage of films or optical layers of the type described above isthat relatively low efficiency is achieved in the surface, in particularwhen they are used in a light fixture to produce planar light. Inaddition, a light distribution curve (LDC), such as that frequentlysought for light fixtures to illuminate surfaces or surface lightfixtures, also cannot be achieved by means of such a film. In addition,the shaping of the radiated light beam in particular in the case oflight sources which emit undirected light, such as organiclight-emitting diodes (OLED), cannot be sufficiently efficient andprecise.

Against this background, it is the object of the present invention topropose an optical layer or a light fixture which suppresses glare withrelatively high efficiency in the illumination of a surface and whichcan be used efficiently for undirected or partially directed lightsources.

BRIEF SUMMARY OF THE INVENTION

The object is achieved according to the invention by an optical layer,as defined by the features of independent claim 1, and by a lightfixture, as defined by the features of independent claim 12.Advantageous alternative embodiments of the invention arise from thedependent claims.

The essence of the invention consists in the following: An optical layermade from a light-permeable material comprises a surface and an opticalmicrostructure having a plurality of elevations. The elevations of themicrostructure protrude from a reference plane, which is parallel to thesurface. The elevations of the microstructure each have a flank sectionwhich adjoins the reference plane and forms a uniform angle with thereference plane. The uniform angle is in a range from about 10° to about26° or in a range from about 13° to about 23° or in a range from about15° to about 20°.

The surface of the optical film can be the side of the film, on whichthe elevations are located. Or it can also be the opposite side of theoptical layer, which is typically designed to be flat. In an embodiment,the surface can be at the height of the peaks of the elevations. In thiscase, the reference plane is parallel and at an interval to the surface.In another embodiment, the surface can also be within the referenceplane. The surface is then parallel to the reference plane but not at aninterval to it. Typically, the surface and also the reference planeextend almost orthogonally to a main or average emission direction of alight fixture in which the optical layer is used. In many applicationssuch as ceiling light fixtures or floor light fixtures, the main oraverage emission direction is vertical and the surface or referenceplane is correspondingly horizontal. The elevations in this regardtypically protrude from the surface.

In relation to the optical layer, the term “light-permeable” can relatein particular to an attenuated or non-attenuated permeability of thelight generated by a lighting means of a light fixture.

In relation to the flank section of one of the elevations, the term“uniform” relates to the fact that the elevation forms a singlesubstantially same angle in the circumferential direction with thereference plane. In this regard, there may be tolerance deviationsarising, for example, for production reasons, which are still deemed tobe uniform in this respect. For example, there can be such tolerancedeviations in a range of up to about 1°.

The optical layer according to the invention enables a light fixture toeffectively obtain high efficiency in a surface or to achieve a highlight output rate (LOR). At the same time, it enables effective andprecise shaping of the light being radiated from the light fixture, inparticular even if the light fixture has an undirected or partiallydirected light source, such as one or more organic light-emitting diodes(OLED) for example. Thus a preferred light distribution curve (LDC) canbe achieved by the uniform angle of the flank sections of the elevationsin the stated ranges. For example, the radiated light can also be shapedasymmetrically or in a wing-like manner. In particular, the glare of thelight fixture can be efficiently suppressed in this way.

According to known standards such as DIN EN 12464-1 of the GermanInstitute for Standardization, the term “glare suppression” can refer tothe fact that, for certain applications of light fixtures, the lightradiated in all lighting angles greater than 65°, when measured inrelation to the vertical line directed downwards, must not exceed alight density of 3000 Candela per square metre (cd/m²).

Furthermore, the optical layer according to the invention from anaesthetic point of view can be advantageous as the microstructures arediscernible only very limitedly or not at all with the naked eye. Aninconspicuous clean appearance can thereby be achieved. The relativelystrong glare suppression and light guiding of the layer is also notaesthetically visible; rather, the optical layer can simply visuallyappear as diffused. This offers many possible applications in design,for example in architecturally integrated lighting. Various LDC can alsobe realised with the same aesthetics. The “tilting effect” that occurswith known lenses which have a macrostructure can also be prevented withthe optical layer. In this regard, “tilting effect” can mean aperception of structures or geometries. In particular, this term canrefer to the fact that the illumination surface image produced changessuddenly, i.e. abruptly and not smoothly, at a certain visual angle.

The term “optical layer” within the meaning of the invention can referto a relatively large-area thin structure. Such structures typicallyhave a much larger surface in relation to the thickness. For example,such structures can have a thickness of less than 1 millimetre (mm) andtypically less than 0.1 mm. The associated surface can be virtually anysize. For example, it can be at least 5 centimetres (cm) by 5 cm. In thecase of the optical layer, this gives a ratio of surface to thickness ofat least about 25,000 or typically at least about 250,000.

In a preferred embodiment, the optical layer is formed as an integrallayer of an optical part. For example, such an optical part can be atransparent lens. In such a lens, the optical layer with itsmicrostructure can be moulded directly into a solid or also mouldablesubstrate of the lens. The microstructure can also, for example, be cut,milled or produced using laser ablation in the substrate of the lens. Orthe entire lens can be produced together with the optical layer using aninjection moulding or injection compression moulding process. Theoptical layer is integrated into such a single-piece lens, which enableseasy handling and ease of use.

In another preferred embodiment, the optical layer is formed as a film.Such films according to the invention can be produced simply andefficiently. They can also be used flexibly. For example, they can becut relatively easily to the shape of an associated lens or anothercomponent of a light fixture. In addition, they can also adapt to theform of the lens or light fixture, for example such as a curvature.Furthermore, such films can also be relatively robust, which enableseasy handling over a long service life.

Optical layers, in particular in the form of films, can be produced fromdifferent materials. In particular, films made of plastic can beefficiently and flexibly produced. Here, such films are preferablyproduced from a material having a refractive index in a range of about1.3 to about 1.7, such as from a plastic like a polycarbonate.Alternative plastics can be, for example, polyethylene or polymethylmethacrylate. In this context, the term “refractive index” is understoodto be an optical material property which indicates the factor by whichthe wavelength and the phase speed of light in a material are less thanin a vacuum. In combination with the uniform angle according to theinvention, films from such materials enable the effects and advantagesof the invention described above to be particularly efficientlyachieved.

Films made of plastic or polycarbonate can be provided withmicrostructures of the type according to the invention in an efficientand precise manner. For example, such microstructures can be formed onor in the plastic using laser ablation, hot stamping, ultravioletcasting, injection moulding, press forming or a generatively structuringmethod such as 3D printing. For series produced films, it can also beexpedient to produce a master and to produce the films by means ofreproduction, for example in a roll-to-roll method. To produce themaster with the microstructure, laser ablation, milling or micromilling,electron beam processing or generative structuring such as 3D printing,for example, can be used.

The elevations of the microstructure of the optical layer are preferablyeach shaped as a cone, a prism, a taper or a pyramid. Such shapesenable, in terms of geometry, a relatively simple design of theelevations with clearly defined flank sections in each case. The uniformangles can thus be relatively easily implemented. In addition, an LDCcan thus be precisely predetermined.

The elevations of the microstructure preferably have a hexagonal basearea. The term “base area” can be understood in particular as thecross-section of the elevation at the height of the reference plane inrelation to the elevations. Elevations having hexagonal base areas canenable large or maximum loading of the optical layer with elevations inan efficient manner. In addition, the proportion of zones of the opticallayer which have no intended light-shaping effect can also be minimised.The optical layer can thus have relatively high efficiency in terms ofthe light-shaping or light-directing effect.

The elevations of the microstructure of the optical layer preferablyhave a rounded peak. The term “peak” can be understood in the context ofthe elevations to be a region which faces away from the reference planeor farthest from this. The peak of an elevation can be opposite its basearea. Such a rounded peak can help to minimise or prevent undesiredcolour effects or rainbow effects. It can be achieved in that angularshapes or transitions in the microstructure are reduced or avoided. Therounded peaks of the elevations preferably each adjoin their flanksections.

The elevations preferably each comprise a base area corresponding to thehexagonal base area, which has a maximum diameter within a range fromabout 5 μm to about 250 μm or in a range from about 50 μm to about 200μm or in a range from about 150 μm to about 190 μm. In addition, theelevations preferably each have a height within a range from about 5 μmto about 100 μm or in a range from about 20 μm to about 80 μm or in arange from about 30 μm to about 60 μm. For elevations each having a basearea and a peak, the height can be defined by the distance between thebase area and the peak. Elevations dimensioned such as a microstructureenable the optical layer to produce a preferred effect andsimultaneously be able to be relatively efficiently produced.

The uniform angle can be between individual elevations or between groupsof elevations. This means the stated angles are uniform per elevationbut vary among elevations. This can enable flexible adapting of an LDC.However, all elevations of the microstructure of the optical layerpreferably have a same uniform angle. The term “same” in relation touniform angles can refer to the fact that all elevations have anidentical uniform angle. Thus tolerance deviations arising, for example,for production reasons can occur, which are still deemed to be same inthis sense. For example, such tolerance deviations can have a value in arange of up to about 1°. An optical layer designed as such efficientlyenables a preferred or intended effect to be homogeneously produced.

Another aspect of the invention relates to a light fixture having alighting means and an optical layer as described above. Light can beradiated in a substantially undirected or partially directed manner bythe lighting means. The optical layer covers the lighting means in aradiation direction of the light fixture. The lighting means can forexample be an OLED or an OLED field. Alternatively, it can be anilluminating diode equipped with a light-diffusing lens or a field ofsuch illuminating diodes.

The term “illuminating diode” can be taken to be synonymous withlight-emitting diode (LED). The illuminating diodes in one view can, forexample, have a round, elliptic, square, or rectangular shape. They canbe attached on a circuit board, which can additionally be equipped withan electronic control system to operate the illuminating diodes.

The term “circuit board” can refer in this context to a printed circuitboard (PCB), which is a carrier for electronic components. In general,circuit boards are used for mechanical fixation and electronicconnection of electronic components. Circuit boards or printed circuitboards usually consist of an insulating material having conductingconnections adhering thereto (conductor paths). Fibre-reinforced plasticis prevalent as the insulating material. The conductor paths arenormally etched from a thin layer of copper. The components are solderedonto soldering pads or into solder land. Larger components can also beattached to the printed circuit board by means of cable ties, adhesiveor screw connections.

The term “undirected” in relation to the lighting means of the lightfixture can refer to the light being radiated in a certain direction ina non-predefined manner, but rather in a certain range in variousdirections. Undirected light can also be described as diffuse light orcomprise such. This term can in particular be understood to mean thatthe lighting means radiates light in a certain range in a random orundefined direction. A partially directed light fixture can also beincluded therein, as long as there is a proportion of undirected lightin the above sense.

With a light fixture according to the invention, the effects andadvantages explained above in relation with the optical layer can berealised in an efficient manner. The optical layer in this regard can beintegrally implemented into a transparent lens. Alternatively, it can beattached to a solid part of the lens. For example, the optical layer canbe applied to the solid part or adhered to this. When adhering theoptical layer to the solid part of the lens, care must be taken toensure that the adhesive used also has a refractive index. In order notto affect the lighting design of the optical layer, an adhesive or gluewith a refractive index as close to 1 as possible is preferably used. Inparticular, the light fixture can be preferably formed as a surfacelight fixture. In this regard, it can have a field of OLEDs or LEDs asthe lighting means.

The light fixture can be assembled in a stacked manner. The light sourcecan be separated in the process by an air gap from the optical layer,thus forming a stack. Or the optical layer can be attached to thelighting means by means of an adhesive so that the lighting means,adhesive and optical layer form a stack. Such a stacked constructionenables a compact design.

The optical layer is preferably arranged in the light fixtureimmediately adjacent to the lighting means. The term “immediatelyadjacent” can in this context refer to the optical layer being locatedas close as technically practical or feasible to the lighting means. Itis possible for the optical layer to be adapted to the shape of thelight fixture or specific components thereof in that the optical filmcan be designed relatively thinly, adjustably and/or flexibly by meansof the microstructure according to the invention. The light fixture canthus be extremely compact, which can be advantageous in manyapplications.

The optical layer according to the invention and the inventive lightfixture can, for example, be advantageous or used in the followingfields of application: architectural lighting applications, theatrelighting applications and general lighting applications. The fields ofuse also include underwater lighting applications such as in swimmingpools, fountains or spa pools, traffic lighting applications, vehiclelighting applications, medical lighting applications such as inhospitals, office and school lighting applications, retail and shoplighting applications and general industrial lighting applications.

The general illumination applications as listed above can be private,commercial and industrial lighting applications. There might be thefollowing characteristics: Light is used in the visible range with awavelength of between 350 mm and 850 nm, the lights are standardised andreplaceable, the lights are produced according to the IEC/PAS 62717standard “Performance requirements—LED modules for general lighting” orthe standard “IEC/PAS 62722 Performance requirements—LED luminaries forgeneral lighting”, the lights include intelligence such as sensors andcommunication cells in order to provide connected lighting, and/or thelights have a general lighting purpose and can be categorisedfunctionally and decoratively.

The traffic lighting applications as listed above can be advancedlighting applications, with which the intention is to provide servicesrelating to different types of transport and traffic management. Theycan allow different users to be better informed and allow networks to beused more safely, smartly and with more coordination. For example, suchtraffic lighting applications can be found in intelligent transportnetworks (ITS) in all kinds of transport. In the EU Directive 2010/40/EU(7 Jul. 2010), it is thus defined what information and communicationtechnologies are used in ITS systems in fields such as roadtransportation, including infrastructure, vehicles and users, and intraffic or mobility management, and interfaces for other types oftransportation.

The vehicle lighting applications as listed above can be all lightingapplications which provide light inside and outside private vehicles andlight-duty and heavy-duty utility vehicles. Such applications caninclude the following, for example: Front and rear lights, visibility,signalling and identification lights, emergency warning devices,interior and comfort lighting, including dispersion lighting andin-service-vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous embodiments of the invention arise from thefollowing description of exemplary embodiments of the invention withreference to the schematic drawing. In particular, the optical layeraccording to the invention and the light fixture according to theinvention are described below in more detail with reference to theattached schematic drawings on the basis of exemplary embodiments. Shownare:

FIG. 1 shows a perspective view of an exemplary embodiment of a film asan optical layer according to the invention;

FIG. 2 shows a side view of the film from FIG. 1;

FIG. 3 shows a perspective view of an embodiment of a light fixtureaccording to the invention with the film from FIG. 1; and

FIG. 4 shows a front view of the light fixture from FIG. 3.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Certain expressions are used in the following description for practicalreasons and must not be construed as limiting. The words “right”,“left”, “down” and “up” designate directions in the drawing to whichreference is made. The expressions “inward”, “outward”, “below”,“above”, “left”, “right”, or the like are used to describe thearrangement of designated parts relative to one another, the movement ofdesignated parts relative to one another, and the directions toward oraway from the geometric centre of the invention as well as named partsof same, as depicted in the figures. These relative spatial indicationsalso comprise positions and orientations other than the ones depicted inthe figures. For example, if a part depicted in the figures is turnedaround, then elements or features described as “below” are then “above”.The terminology comprises the words expressly mentioned above,derivatives thereof, and words of similar meaning.

In order to avoid repetitions in the figures and in the associateddescription of the different aspects and exemplary embodiments, certainfeatures should be understood as common to different aspects andexemplary embodiments. The omission of an aspect from the description orfrom a figure does not mean that this aspect is lacking in theassociated exemplary embodiment. Instead, such an omission may be madefor the sake of clarity and for avoiding repetitions. The proportions ofthe parts represented in the figures can also deviate from the actualproportions. For example, the thickness or height of the film in thefigures is represented in an enlarged view in relation to its dimensionor area. In particular, certain dimensions can be represented in anenlarged view so that individual features are more clearly visible.

FIG. 1 schematically shows a film 1 as an exemplary embodiment of anoptical layer according to the invention. Film 1 is, for example,produced from polycarbonate as a light-permeable material. It comprisesa flat base body 12 and a surface 13. The flat base body 12 is providedon the side of the surface 13 with a microstructure 11, which comprisesa plurality of almost hill-shaped or almost cone-shaped elevations 111.The elevations 111 have flank sections 112, which each merge into arounded peak 113. The flank sections 112 thus adjoin the associatedrounded peaks 113. The elevations 111 are distributed uniformly andevenly over the surface 13. The microstructure 11 can be formed usingpress forming in a roll-to-roll method or using laser ablation inpolycarbonate.

The following definition applies to the entire remainder of thedescription: If there are reference signs are in a figure for the sakeof graphic clarity, but not mentioned in the immediately associateddescriptive text, then reference shall be made to the explanationthereof in preceding figure descriptions. Furthermore, if referencesigns are mentioned in the descriptive text immediately associated witha figure, but are not present in the associated figure, reference shallbe made to the preceding and following figures. Similar reference signsin two or more figures stand for similar or the same elements.

As can be seen in FIG. 2, film 1 has a reference plane 15 whichcorresponds to the surface 13 and from which the elevations 111 protrudefrom the microstructure 11. The flank sections 112 of the elevations 111are formed straight from the side. They adjoin the reference plane 15 oremanate from same. The flank sections 112 and the reference plane 15have a uniform angle α, which is constant over the entire film 1 and theentire amount of individual elevations 111. The uniform angle α is 17°,wherein there can be certain tolerance deviations, for example, forproduction reasons.

In FIG. 3, an embodiment of a light fixture 2 according to the inventionis schematically shown in which the film 1 is arranged. The lightfixture 2 is formed as a ceiling light, which emits light in a downwardsvertical radiation direction 24. The light fixture 2 comprises a housing22, in which a lighting means is arranged with an organic illuminatingdiode (OLED lighting means) 21. The OLED lighting means 21 radiateslight in an undirected manner from its lower surface. Likewise in thehousing 22, the film 1 is attached parallel to the OLED lighting means21, wherein the microstructure 11 faces away from the OLED lightingmeans 21. The film 1 completely covers the OLED lighting means 21 on itslight-emitting lower surface or in the radiation direction 24.

At the bottom, the housing 22 is enclosed by a transparent lens 23. Thelens 23 covers the film 1 from the outside. When the light fixture 2 isoperated, the OLED lighting means 21 radiates its undirected light onthe underside. This light penetrates the film 1 and is directed andshaped by its microstructure 11. In particular, the shape of theelevations 111 with the uniform angle α of 17° enables a high degree oflight efficiency to be produced in the surface or a high light outputrate (LOR) to be achieved. At the same time, it also enables effectiveand precise production of a preferred light distribution curve (LDC). Inparticular, the glare of the light fixture 2 can be sufficientlysuppressed in this way. Using the rounded peaks 113 of the elevations111, undesired rainbow effects can also be minimised.

FIG. 4 shows the light fixture 2 from below or from its lens 23. Here,it can be seen through the transparent lens 23 that the elevations 111of the microstructure 11 of the film 1 have a basic hexagonal form. Sucha basic form enables the film 1 to be densely or completely providedwith elevations 111.

Although the invention is shown and described in detail by means of thefigures and the associated description, this representation and thisdetailed description are to be understood as illustrative and exemplary,but not as limiting the invention. In order not to embellish theinvention, in certain cases well-known structures and techniques may notbe shown and described in detail. Obviously, persons skilled in the artcan make changes and modifications without exceeding the scope of thefollowing claims. In particular, the present invention covers furtherexemplary embodiments with any combinations of features that may deviatefrom the explicitly described combinations of features.

The present disclosure also comprises embodiments with any combinationof features that are mentioned or shown before or after the differentembodiments. It also comprises individual features in the figures, evenif they are shown therein in relation to other features and/or notmentioned above or below. The alternatives to embodiments and individualalternatives to the features thereof described in the figures and in thedescription may also be excluded from the subject matter of theinvention or from the disclosed subjects. The disclosure comprisesembodiments that exclusively comprise the features described in theclaims or in the exemplary embodiments, as well as embodiments thatcomprise additional other features.

In addition, the expression “comprise” and derivatives thereof do notexclude other elements or steps. The indefinite article “a” or “an” andderivatives thereof likewise do not exclude a plurality. The functionsof a plurality of the features cited in the claims can be fulfilled by aunit or by a step. The mere fact that certain dimensions are listed independent claims that are different to one another does not indicatethat a combination of these dimensions cannot be used advantageously. Inparticular, the terms “substantially”, “about”, “approximately” and thelike used in connection with a property or a value also define theproperty precisely or define the value precisely. When used inconnection with a given numerical value or range, the terms “about” and“approximately” can refer to a value or range that lies within 20%,within 10%, within 5%, or within 2% of the given value or range. Allreference signs in the claims are not to be understood as limiting thescope of the claims.

1. An optical layer made from a light-permeable material, the opticallayer comprising: a surface; and an optical microstructure having aplurality of elevations, wherein the plurality of elevations of theoptical microstructure protrude from a reference plane, which isparallel to the surface, wherein the plurality of elevations of theoptical microstructure each have a flank section which adjoins thereference plane and forms a uniform angle with the reference plane, andwherein the uniform angle is in a range from about 10° to about 26°. 2.The optical layer according to claim 1, in which the surface is in thereference plane.
 3. The optical layer according to claim 1, wherein theoptical layer is designed as a film.
 4. The optical layer according toclaim 3, wherein the optical layer is produced from a material having arefractive index in a range from about 1.3 to about 1.7.
 5. The opticallayer (1) according to claim 1, wherein the plurality of elevations ofthe optical microstructure are each designed as cones, tapers, prisms orpyramids.
 6. The optical layer according to claim 1, wherein theplurality of elevations of the optical microstructure have a hexagonalbase area.
 7. The optical layer according to claim 1, wherein theplurality of elevations of the optical microstructure each have arounded peak.
 8. The optical layer according to claim 7, wherein therounded peaks of the plurality of elevations each adjoin the flanksections.
 9. The optical layer according to claim 1, wherein theplurality of elevations each comprise a base area, which has a maximumdiameter which is within a range from about 5 μm to about 250 μm or in arange from about 50 μm to about 200 μm or in a range from about 150 μmto about 190 μm.
 10. The optical layer according to claim 1, wherein theplurality of elevations each have a height which is within a range fromabout 5 μm to about 100 μm or in a range from about 20 μm to about 80 μmor in a range from about 30 μm to about 60 μm.
 11. The optical layeraccording to claim 1, wherein all elevations of the opticalmicrostructure have the same uniform angle.
 12. A light fixture having alighting means and an optical layer according to claim 1, wherein lightcan be radiated in a substantially undirected manner by the lightingmeans and wherein the optical layer covers the lighting means in aradiation direction of the light fixture.
 13. The light fixtureaccording to claim 12, wherein the light fixture is formed as a surfacelight fixture.
 14. The light fixture according to claim 12, wherein theoptical layer is arranged immediately adjacent to the lighting means.15. The optical layer according to claim 1, wherein the uniform angle isin the range from about 13° to about 23°.
 16. The optical layeraccording to claim 1, wherein the uniform angle is in the range fromabout 15° to about 20°.
 17. The optical layer according to claim 4,wherein the material is a polycarbonate.